I better let Wikipedia tell you what the Krampus and Knecht Ruprecht are all about:

The Companions of Saint Nicholas (or Father Christmas) are a group of closely related figures who accompany St. Nicholas in many European traditions. The tradition is particularly strong amongst the Germanic peoples, with some regional expression in the U.S. (largely from European ethnic groups).

The most recognized companion, especially outside of Europe, is Knecht Ruprecht, which translates as Farmhand Ruprecht or Servant Ruprecht. Other companions include Krampus (Austria, Bavaria, Croatia, Slovenia, Hungary [spelled Krampusz]), Klaubauf (Bavaria), Bartel (Styria), Pelzebock, Pelznickel, Belzeniggl, Belsnickel (Pennsylvania), Schmutzli (Switzerland), Rumpelklas, Bellzebub, Hans Muff, Drapp or Buzebergt (Augsburg), Hanstrapp (Alsace, East of France) and Le Père Fouettard (Northern France). In the Czech Republic, St. Nicholas or Svatý Mikuláš is accompanied by the Čert (Devil) and Anděl (Angel). These servants are often associated with, but are distinct from Saint Nicholas’ helpers in the Netherlands and Flanders (called Zwarte Piet, meaning Black Pete(r) in English).

Make sure to read the whole entry for loads of details.

As you can see from the last image this tradition is very much alive here in Europe and I can assure you that tonight many kids and some adults gonna crap into their pants when St. Niklaus and a wild Krampus hits their home …